Human brain in the context of Anterior pituitary

Humans, scientifically known as Homo sapiens, are primates that belong to the biological family of great apes and are characterized by hairlessness, bipedality, and high intelligence. Humans have large brains compared to body size, enabling more advanced cognitive skills that facilitate successful adaptation to varied environments, development of sophisticated tools, and formation of complex social structures and civilizations.

Humans are highly social, with individual humans tending to belong to a multi-layered network of distinct social groups – from families and peer groups to corporations and political states. As such, social interactions between humans have established a wide variety of values, social norms, languages, and traditions (collectively termed institutions), each of which bolsters human society. Humans are also highly curious: the desire to understand and influence phenomena has motivated humanity's development of science, technology, philosophy, mythology, religion, and other frameworks of knowledge; humans also study themselves through such domains as anthropology, social science, history, psychology, and medicine. As of 2025, there are estimated to be more than 8 billion living humans.

Technology is the application of conceptual knowledge to achieve practical goals, especially in a reproducible way. The word technology can also mean the products resulting from such efforts, including both tangible tools such as utensils or machines, and intangible ones such as software. Technology plays a critical role in science, engineering, and everyday life.

Technological advancements have led to significant changes in society. The earliest known technology is the stone tool, used during prehistory, followed by the control of fire—which in turn contributed to the growth of the human brain and the development of language during the Ice Age, according to the cooking hypothesis. The invention of the wheel in the Bronze Age allowed greater travel and the creation of more complex machines. More recent technological inventions, including the printing press, telephone, and the Internet, have lowered barriers to communication and ushered in the knowledge economy.

In psychoanalytic theory, fantasy is a broad range of mental experiences, mediated by the faculty of imagination in the human brain, and marked by an expression of certain desires through vivid mental imagery. Fantasies are generally associated with scenarios that are impossible or unlikely to happen.

Sexual fantasies are a common type of fantasy.

Materialism is a form of philosophical monism in metaphysics, according to which matter is the fundamental substance in nature, and all things, including mental states and consciousness, are results of material interactions. According to philosophical materialism, mind and consciousness are caused by physical processes, such as the neurochemistry of the human brain and nervous system, without which they cannot exist. Materialism directly contrasts with monistic idealism, according to which consciousness is the fundamental substance of nature.

Materialism is closely related to physicalism—the view that all that exists is ultimately physical. Philosophical physicalism has evolved from materialism with the theories of the physical sciences to incorporate forms of physicality in addition to ordinary matter (e.g. spacetime, physical energies and forces, and exotic matter). Thus, some prefer the term physicalism to materialism, while others use them as synonyms. Materialism is also related to naturalism—the position that only natural laws and forces operate in the universe.

Neurology (from Greek: νεῦρον (neûron), "string, nerve" and the suffix -logia, "study of") is the branch of medicine dealing with the diagnosis and treatment of all categories of conditions and disease involving the nervous system, which comprises the brain, the spinal cord and the peripheral nerves. Neurological practice relies heavily on the field of neuroscience, the scientific study of the nervous system, using various techniques of neurotherapy.

A neurologist is a physician specializing in neurology and trained to investigate, diagnose and treat neurological disorders. Neurologists diagnose and treat myriad neurologic conditions, including stroke, epilepsy, movement disorders such as Parkinson's disease, brain infections, autoimmune neurologic disorders such as multiple sclerosis, sleep disorders, brain injury, headache disorders like migraine, tumors of the brain and dementias such as Alzheimer's disease. Neurologists may also have roles in clinical research, clinical trials, and basic or translational research. Neurology is a nonsurgical specialty, its corresponding surgical specialty is neurosurgery.

Visual or vision impairment (VI or VIP) is the partial or total inability of visual perception. In the absence of treatment such as corrective eyewear, assistive devices, and medical treatment, visual impairment may cause the individual difficulties with normal daily tasks, including reading and walking. The terms low vision and blindness are often used for levels of impairment which are difficult or impossible to correct and significantly impact daily life. In addition to the various permanent conditions, fleeting temporary vision impairment, amaurosis fugax, may occur, and may indicate serious medical problems.

The most common causes of visual impairment globally are uncorrected refractive errors (43%), cataracts (33%), and glaucoma (2%). Refractive errors include near-sightedness, far-sightedness, presbyopia, and astigmatism. Cataracts are the most common cause of blindness. Other disorders that may cause visual problems include age-related macular degeneration, diabetic retinopathy, corneal clouding, childhood blindness, and a number of infections. Visual impairment can also be caused by problems in the brain due to stroke, premature birth, or trauma, among others. These cases are known as cortical visual impairment. Screening for vision problems in children may improve future vision and educational achievement. Screening adults without symptoms is of uncertain benefit. Diagnosis is by an eye exam.

Laughter is a typically pleasant physical reaction and emotion consisting usually of rhythmical, usually audible contractions of the diaphragm and other parts of the respiratory system. It is a response to certain external or internal stimuli. Laughter can rise from such activities as being tickled, or from humorous stories, imagery, videos or thoughts. Most commonly, it is considered an auditory expression of a number of positive emotional states, such as joy, mirth, happiness or relief. On some occasions, however, it may be caused by contrary emotional states such as embarrassment, surprise, or confusion such as nervous laughter or courtesy laugh. Age, gender, education, language and culture are all indicators as to whether a person will experience laughter in a given situation. Other than humans, some other species of primate (chimpanzees, gorillas and orangutans) show laughter-like vocalizations in response to physical contact such as wrestling, play chasing or tickling.

Laughter is a part of human behavior regulated by the brain, helping humans clarify their intentions in social interaction and providing an emotional context to conversations. Laughter is used as a signal for being part of a group—it signals acceptance and positive interactions with others. Laughter is sometimes seen as contagious and the laughter of one person can itself provoke laughter from others as a positive feedback.

A complex system is a system composed of many components that interact with one another. Examples of complex systems are Earth's global climate, organisms, the human brain, infrastructure such as power grid, transportation or communication systems, complex software and electronic systems, social and economic organizations (like cities), an ecosystem, a living cell, and, ultimately, for some authors, the entire universe.

The behavior of a complex system is intrinsically difficult to model due to the dependencies, competitions, relationships, and other types of interactions between their parts or between a given system and its environment. Systems that are "complex" have distinct properties that arise from these relationships, such as nonlinearity, emergence, spontaneous order, adaptation, and feedback loops, among others. Because such systems appear in a wide variety of fields, the commonalities among them have become the topic of their independent area of research. In many cases, it is useful to represent such a system as a network where the nodes represent the components and links represent their interactions.

The cerebrum (pl.: cerebra), telencephalon or endbrain is the largest part of the brain, containing the cerebral cortex (of the two cerebral hemispheres) as well as several subcortical structures, including the hippocampus, basal ganglia, and olfactory bulb. In the human brain, the cerebrum is the uppermost region of the central nervous system. The cerebrum develops prenatally from the forebrain (prosencephalon). In mammals, the dorsal telencephalon, or pallium, develops into the cerebral cortex, and the ventral telencephalon, or subpallium, becomes the basal ganglia. The cerebrum is also divided into approximately symmetric left and right cerebral hemispheres.

With the assistance of the cerebellum, the cerebrum controls all voluntary actions in the human body.

The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is continuous with the thalamus of the diencephalon through the tentorial notch, and sometimes the diencephalon is included in the brainstem.

The brainstem is very small, making up around only 2.6 percent of the brain's total weight. It has the critical roles of regulating heart and respiratory function, helping to control heart rate and breathing rate. It also provides the main motor and sensory nerve supply to the face and neck via the cranial nerves. Ten pairs of cranial nerves come from the brainstem. Other roles include the regulation of the central nervous system and the body's sleep cycle. It is also of prime importance in the conveyance of motor and sensory pathways from the rest of the brain to the body, and from the body back to the brain. These pathways include the corticospinal tract (motor function), the dorsal column-medial lemniscus pathway (fine touch, vibration sensation, and proprioception), and the spinothalamic tract (pain, temperature, itch, and crude touch).

White matter refers to areas of the central nervous system that are mainly made up of myelinated axons, also called tracts. Long thought to be passive tissue, white matter affects learning and brain functions, modulating the distribution of action potentials, acting as a relay and coordinating communication between different brain regions.

White matter is named for its relatively light appearance resulting from the lipid content of myelin. Its white color in prepared specimens is due to its usual preservation in formaldehyde. It appears pinkish-white to the naked eye otherwise, because myelin is composed largely of lipid tissue veined with capillaries.

The neocortex, also called the neopallium, isocortex or six-layered cortex, is a set of layers of the mammalian cerebral cortex involved in higher-order brain functions such as sensory perception, cognition, generation of motor commands, spatial reasoning, and language. The neocortex is further subdivided into the true isocortex and the proisocortex.

In the human brain, the cerebral cortex consists of the larger neocortex and the smaller allocortex, respectively taking up 90% and 10%. The neocortex is made up of six layers, labelled from the outermost inwards, I to VI.

The allocortex (from Latin allo-, meaning other, and cortex, meaning bark or crust), or heterogenetic cortex, is one of the two types of cerebral cortex in the brain, together with the neocortex. In the human brain, the allocortex is the much smaller area of cortex taking up just 10%; the neocortex takes up the remaining 90%. It is characterized by having just three cortical layers (one main neural layer), in contrast with the six cortical layers of the neocortex. There are three subtypes of allocortex: the paleocortex, the archicortex, and the periallocortex—a transitional zone between the neocortex and the allocortex.

The specific regions of the brain usually described as belonging to the allocortex are the olfactory system and the hippocampus.